When the OSD pool size is unset it defaults to 3, while we only
have a single OSD in CI so the pools are created but not writable.
We did set the default pool size to 1 in the non-containerized
scenarios but apparently missed it in the containerized version.
Change-Id: I1ac1fe5c2effd72a2385ab43d27abafba5c45d4d
Closes-Bug: #1710773